Stereoselective Synthesis Of α-2-deoxy Glycosides Via Iron Catalysis

2-Deoxysugars occurring broadly in bioactive natural products and drugs exert various pharmacological effects.However,2-deoxyglucosides are difficult to obtain in large quantities directly from nature,and in recent years,the efficient synthesis of 2-deoxyglycosides has attracted more and more chemists’ attention.Due to the complex structure of natural products and the lack of participation of C-2 neighboring groups in the synthesis process of 2-deoxyglycosides,obtaining 2-deoxyglycosides stereoselectively is challenging.In this thesis,we have developed a novel α-selective 2-deoxyglycosylation method from glycals catalyzed by iron.This novel approach enabled facile access to 26 alkyl 2-deoxyglycosides and 19 aryl 2-deoxyglycosides.In addition to various acceptors(alcohols,phenols,monosaccharides),a wide range of glycal donors(D-galactal protected by 3 different functional groups L-arabinal,and L-fucal)were tolerated well,giving 2-deoxyglycosides in high yields with exclusive α-selectivity,and achieving gram scale reaction.Unlike the typical noble-metal catalysis relying on the coordination between metal and olefin of glycals,this approach could generate high selectivity via in situ anomerization.In particular,the synthetic utility and advantage of this strategy have been demonstrated by the modification of 6 natural products and the construction of tetrasaccharide.In the application of the method,structural modifications were carried out on 6 natural products with high biological activity,such as sterols,estrone and so on.At the same time,from simple monosaccharide to complex long-chain deoxytetrasaccharide,this approach provides a synthetic route for the rapid synthesis of long-chain 2-deoxy oligosaccharide,which provides a new methodological reference for the stereoselective synthesis of 2-deoxyglycosides and the synthesis of natural products and pharmaceutical preparations.